A leading conservationist says moves to demolish a mansion linked to the novelist Evelyn Waugh are a “tragedy” for Welsh heritage.

Mark Baker, who sits on the National Trust’s Committee for Wales, said the decision to demolish 1840s site Plas Dulas, in Conwy, North Wales, is part of a pattern of neglect of 19th century heritage.

Waugh, who wrote Brideshead Revisited and Scoop, is said to have used the house as his inspiration for the boy’s school Llanabba in his 1928 novel Decline and Fall.

The novelist worked at Arnold House, a school located further up a hill where Plas Dulas is situated.

Mr Baker said: “Waugh was part of this literary circle from Oxbridge where the owner of Plas Dulas (Professor Richard Dawkins) was a famous archaeologist and lecturer.

“So they’re all inter-connected and Waugh is said to have stayed at Plas Dulas.”

Owner of the site, builder Alex Davies, who was last month given permission by Conwy Council to demolish the house and construct 15 homes, disputes the strength of the connection to Waugh.

He said: “He used to be a teacher in a building further up the hill for about six months, but he never actually went into the building (Plas Dulas).”

Mr Davies said the building, which is not listed, has been derelict for two to three decades, with slates stolen and interiors gutted.

“Thirty years of rain have basically destroyed the building. It would cost millions upon millions to restore it.”

However, conservation engineer Jon Avent carried out a structural survey in 2010 that concluded the building could be restored.

Mr Baker, 29, who is doing a PhD on Welsh country house architecture, said if Plas Dulas were in England it would be listed.

He maintains post-1840s properties are neglected by Cadw – the conservation arm of the Welsh Government. As a result, much of Wales’ stock of Victorian and Edwardian architecture has failed to attract protection.

Mr Baker pointed to the demolition of Llandudno’s Penmorfa Hotel in 2008.

The building, dating from the 1870s, was said to have links to Alice in Wonderland author Lewis Carroll.

A Welsh Government spokesperson said because of the greatly-increased number of buildings constructed after 1840 and the much larger numbers that have survived, greater selection is needed to identify the best examples.

“The case for listing Plas Dulas was thoroughly considered in 2010. It was concluded that the building did not satisfy the listing criteria and so could not be listed as a building of special architectural or historic interest. The same criteria for listing apply in England and Wales,” added the spokesperson.